1. Field of the Invention
The invention relates to a circular rolling mill used for shaping annular workpieces, such as forged metal pulley or wheel blanks or other similar workpieces.
2. The Prior Art
It is known, for example from FR-A-2 014 080, to use a circular rolling mill with four rollers to form annular workpieces. Two cylindrical rollers are used to work respectively the radial outer and inner faces of the annular workpiece, while a pair of conical rollers is used to work the front faces of the workpiece. Electric motors are used to rotate at least some of these rollers. These rollers have to be displaced with respect to one another, this being to take account of dimensional variations in the workpiece during its rolling and to exert shaping forces on its inner, outer or front faces. In order to do this, use is made of hydraulic jacks which allow considerable forces to be generated over paths of relatively small amplitude. The use of such jacks makes it necessary to maintain the functioning of a hydraulic power unit and to control distributors for the distribution of the operating oil of the jacks. This requires periodic checks and relatively complex maintenance operations. Oil leaks cannot be ruled out, thus giving rise to the risk of fire.
It is these drawbacks in particular that the invention is intended to overcome by proposing a circular rolling mill, the operation whereof is rendered reliable and the maintenance whereof can be facilitated, without impairing the quality of the rolling obtained or the robustness of the rolling mill.